The present disclosure relates generally to cardiac implant systems and, more particularly, to a cardiac imaging system and method for planning isolation of the left atrial appendage of the heart.
Atrial fibrillation (AF) is an arrhythmia in which the atria (upper chambers of the heart) stop contracting properly as they fibrillate, and is the most common of heart rhythm irregularities. It is estimated that over 2.2 million Americans have been diagnosed with AF, with over 140,000 new cases being diagnosed each year. Patients with AF have a high risk of stroke, and about 15 percent of all strokes occur in people with atrial fibrillation. Each year, about 600,000 Americans suffer a new or recurrent stroke. In 1991, the Framingham study showed that a diagnosis of AF increased the risk of stroke 3 to 5 times higher, rising from 1.5% in the fifth decade of life to over 23% by the eighth decade.
More specifically, previous studies indicate that more than 90 percent of nonrheumatic AF-related strokes result from a blood clot that forms in the left atrial appendage (LAA), a small, thumb-shaped pouch in the heart's left upper chamber. Such clots can block a blood vessel leading to the brain, thereby causing a stroke. Several large randomized trials have shown the efficacy of warfarin, a blood thinner, in reducing the risk of stroke. In clinical practice, however, in over 40 percent of patients the drug is contraindicated or cannot be used because of the side effects, such as bleeding. Another approach to treating AF is a surgical intervention, such as the Maze procedure, in which strategic placement of incisions in both atria stops the formation and the conduction of errant electrical impulses. The maze procedure channels the normal electrical impulse to travel in one direction from the top of the heart to the bottom by producing a scar tissue that permanently blocks the travel routes of the electrical impulses that cause AF, thus eradicating the arrhythmia. In such procedures, the LAA is routinely removed, as recommended in the American College of Cardiology-American Heart Association guidelines.
Recently, in order to provide still an alternative strategy for preventing stroke, minimally invasive techniques involving deliberate occlusion of the LM are being implemented. In particular, a catheter is used to place a blocking device at the mouth of the LAA. The blocking device is a self-expanding metal cage of nitinol that pops open as the metal warms up inside the body. The cage is covered with a membrane, which blocks the atrial appendage and allows normal tissue to grow into the device. In one study of this procedure, called PLAATO (percutaneous left atrial appendage transcatheter occlusion), the patients' implants ranged in diameter from 18 to 32 millimeters with the average procedure time being 92.7 minutes. However, in 25% of those patients, the initial device was removed and replaced with one of a different size. As such, there is a need for an improved system and method for determining an effective roadmap for LAA anatomy and, where appropriate, a roadmap for effective LAA isolation and/or occlusion.